Pitch is how high or low a sound seems, and it is set by the sound’s fundamental frequency: how many times per second it vibrates. In a voice, the vocal folds set the pitch and the throat and mouth shape the tone. A pitch shifter moves both together, which is why small shifts sound natural and large ones do not. To change the key of a recording without changing its speed, shift it by a few semitones with a pitch and speed changer.
In Short
The short version:
- Pitch is the perceived height of a sound; frequency is the measured number of vibrations per second (Hz).
- Doubling the frequency raises the pitch by one octave.
- The vocal folds set the pitch; the vocal tract shapes the tone through its resonances (formants).
- Shifting the pitch moves the formants too; beyond about 3 semitones a voice sounds like someone else.
- Pitch and speed can be changed independently of each other.
Pitch and Frequency: What Is the Difference?
Frequency is a physical measurement: the number of vibrations per second, given in hertz (Hz). Pitch is what we hear: how high or low a sound seems. The two go together, since a higher frequency is heard as a higher pitch, but the relationship is not a straight line. We hear pitch in ratios: every doubling of frequency sounds like the same step, one octave. From 110 Hz to 220 Hz is an octave, and so is 440 Hz to 880 Hz, although the second step is four times as large in hertz.
Music divides each octave into twelve semitones. In the standard tuning system each semitone raises the frequency by about 5.9 percent, and the note A4 is fixed at 440 Hz. That is all you need to name any frequency as a note; the Frequency to Note Converter does the calculation, and Hz to Note explains it step by step.
How the Voice Produces Pitch
When you speak or sing, air from the lungs sets the vocal folds in the larynx vibrating. The rate of that vibration is the fundamental frequency of the voice, often written F0, and it is what we hear as the pitch. Longer, heavier vocal folds vibrate more slowly, which is why adult male voices are typically lower than female voices and children’s voices are higher still. Tightening the folds raises the pitch, much as tightening a guitar string does. The School of Physics at UNSW Sydney describes the mechanism in its introduction to voice acoustics.
Tone Is Not Pitch: Formants
Two people can sing the same note and still sound completely different. The vocal folds produce a buzz that contains the fundamental and a whole series of harmonics above it. On its way out, that sound passes through the throat and mouth, which resonate at certain frequencies and strengthen the harmonics that fall there. These resonances are called formants. They depend on the size and shape of the vocal tract, and they are what make a vowel an “ah” or an “ee” and one voice different from another.
The important point is that the formants are largely independent of the pitch. When you sing a scale on one vowel, the fundamental moves, but the resonances of your vocal tract stay roughly where they are.
Why a Pitch-Shifted Voice Sounds Unnatural
A simple pitch shifter moves everything by the same ratio: the fundamental, the harmonics and the formants. Shift a voice up by an octave and the formants double as well, as if the speaker’s throat and mouth had shrunk to half their size. The ear reads that as a tiny creature, the well-known chipmunk effect. Shifted down, the same voice sounds like someone with an impossibly large head.
With small shifts the effect is hardly noticeable, because real voices differ by that much anyway. Up to two or three semitones, a shifted voice still sounds like the same person. Beyond that, the character changes. Professional tools can shift the pitch while holding the formants in place; simple pitch shifters, including the one on this site, move them together.
| Shift | What you hear |
|---|---|
| ±1 to 3 semitones | Natural; the voice keeps its character |
| ±4 to 6 semitones | Clearly altered: thinner when raised, heavier when lowered |
| ±7 to 12 semitones | A different character altogether: cartoon-like when raised, monster-like when lowered |
How to Change Pitch Without Changing Speed
On a record player or a tape machine, pitch and speed are locked together: play it faster and everything gets higher. Digital processing separates the two. To transpose a song or a recording:
Step 1: Open the Recording
Load your file into the Pitch & Speed Changer. MP3, WAV, FLAC and M4A files work, and nothing is uploaded.
Step 2: Set the Pitch in Semitones
Move the Pitch slider. To take a backing track from C to D, for example, go up 2 semitones; to bring a song down into your range, try -2 or -3 first. Leave Speed at 1.00x and the tempo stays as it was.
Step 3: Listen, Then Adjust the Speed If You Need To
Press Play to check the result. The Speed slider is independent: slow a passage to 0.8x to practice it, or speed up a spoken recording, and the pitch stays where you set it. Download the WAV when it sounds right.
Common Reasons to Change Pitch
- Transposing a backing track so that a song sits in a comfortable key for your voice.
- Matching a sample to the key of a project. Find the key first with the BPM & Key Analyzer.
- Practicing: slowing a fast passage down without lowering it.
- Creative effects: a voice pitched far up or down is unnatural by design, which is exactly what some styles want. If you want pitch and speed to fall together, as on a slowed record, use the Slowed + Reverb Maker.
Change the Pitch of Your Recording
Shift the key by semitones or change the speed, each without affecting the other.
Open the Pitch & Speed ChangerFree, no sign-up, and your files never leave your device.